In recent years, vehicles that travel by electricity (hereinafter, simply referred to as “vehicle”) such as electric vehicles (EV) and plug-in hybrid vehicles (PHEV) have been widespread. Such a vehicle is equipped with a large-capacity storage battery, stores electric energy supplied from the outside in the storage battery, and travels by using the stored electric energy.
Meanwhile, mobile phones (including so-called smart phones, and the like), notebook computers, tablets or the like have been widespread. Such a mobile terminal is also equipped with a storage battery, and charging to the storage battery and discharging from the storage battery are performed.
As a method for supplying power to a storage battery that is mounted in such a vehicle, a mobile terminal, and the like, there is a method for supplying power in a contactless manner using an electromagnetic force between a primary coil of a power supply device and a secondary coil of a power receiving device. In this method, if metal such as a coin is present between the power supply device and the power receiving device, an induced current is generated in the metal by a magnetic flux generated between the power supply device and the power receiving device, and this results in heat generation in the metal. As a result, there is a concern that a case is melted, or fire occurs.
Therefore, a technique for detecting such a foreign metal body (hereinafter, simply referred to as “foreign object”) is disclosed in, for example, PTL 1.
PTL 1 discloses a power supply device which includes a light emitting member and a light receiving member which are provided on a primary coil side, and a light guiding member such as an optical fiber provided on a secondary coil side, if there is no foreign object in a gap between the primary coil and the secondary coil, light from the light emitting member is received by the light receiving member through the light guide member; and if a foreign object is trapped in the gap, light from the light emitting member is blocked by the foreign object and the light is not received by the light receiving member, and the excitation of the primary coil is stopped.